Gram (+) Rods

• Gram Positive Rods


  Bacteria that stain purple with the Gram stain and have a rod-shaped morphology
• Gram (+) Rods

  • Corynebacterium
  • Bacillus
  • Listeria
  • Propionibacterium
  • Lactobacillus
• Corynebacteria


  • Small, slender, pleomorphic rods that stain unevenly
  • Non-motile
  • Uncapsulated
  • Do not form spores
• Corynebacterium diphtheria


  Causes diphtheria
• Immunity - Corynebacterium diphtheria


  Vaccine (formalin treated toxin)<|>DTaP @ infancy with 10-yr interval booster doses
• Bacillus Species

  • Form endospores
  • Strict aerobes or aerotolerant anaerobes (do not require oxygen)
  • Most are found in soil & water
• Bacillus Species

  • B. anthracis
  • B. cereus
• Bacillus anthracis - Immunity and Treatment


  Vaccine for workers in high-risk occupations<|>Post-exposure prophylaxis w/ Ciprofloxacin or Doxycycline

  
• Bacillus cereus


  Uncommonly, other species of bacillus are implicated in opportunistic lesions, particularly following trauma or the placement of artificial devices and catheters<|>Causes food poisoning by means of enterotoxins with either emetic or diarrheal effects
• Listeria

  • Slender, short, w/ peritrichous flagella
  • Do not form spores
  • Sometimes occur as diplobacilli or in short chains, and may be seen within the cytoplasm of host cells in tissue samples
  • Catalase (+)
  • Tumbling motility by light microscopy in liquid medium at 25oC
  • Non-motile at 37oC
  • These characteristics distinguish it from Streptococcus (catalase(-)) or Corynebacterium (non-motile) species, both of which may be confused morphologically with Listeria

  
• Propionibacterium acnes


  Anaerobic or microaerophilic rods of diphtheroid-like morphology<|>Common inhabitants of normal skin, and, in rare instances, have been reported as causes of endocarditis and infections of plastic implants<|>Acne

  
• Lactobacillus


  Part of the commensal flora of human mucous membranes<|>Produce large quantities of lactic acid during fermentation and have been thought to assist in maintaining the acid pH of normal mucous epithelia<|>Acid production by oral lactobacilli may play a role in the progression of dental caries, especially in dentine

  
• Corynebacterium diphtheria


  Bacterium that causes diphtheria
• Epidemiology of Corynebacterium diphtheria

  • Found in the throat and nasopharynx of carriers and in patients with diphtheria
  • Local infection, usually of the throat, and the organism is primarily spread by respiratory droplets, usually by convalescent or asymptomatic carriers
• Pathogenesis of Corynebacterium diphtheria

  Caused by the local and systemic effects of a single exotoxin that inhibits eukaryotic protein synthesis<|>Toxin molecule is a heat-labile polypeptide that is composed of two fragments, A and B
• Clinical Significance of Corynebacterium diphtheria

  • URTI (Upper Respiratory Tract Infection) - thick, grayish, adherent exudate (pseudomembrane) - cell debris and inflammatory products in the throat - coats throat and may extend into nasal passages or respiratory tract, where exudate sometimes obstructs leading to suffocation
  • Cardiac conduction defects & myocarditis leading to congestive heart failure
  • Neuritis of cranial nerves & paralysis of palate or eye
  • Cutaneous diphtheria - puncture wound or cut in the skin can result in introduction into the subcutaneous tissue - chronic, non-healing ulcer with a gray membrane
• Immunity to Corynebacterium diphtheria

  Vaccine (formalin treated toxin) - DTaP @ infancy with 10-yr interval booster doses
• Bacillus anthracis


  Causative agent of anthrax
• Anthrax is a rare disease in the US
• From 1984 to 1997, only 3 cases of cutaneous anthrax were reported
• In 2001, 20 new cases occurred (10 cutaneous & 10 inhalation)
• Anthrax


  • Enzootic disease of worldwide occurrence
  • Domestic herbivores (sheep, goats, and horses) are affected
  • Transmitted to humans by contact with infected animal products or contaminated dust
  • Initiated by the subcutaneous inoculation of spores through incidental skin abrasions
  • Less frequently, the inhalation of spore-laden dust causes a pulmonary form
  • Spores may remain viable for many years in contaminated pastures and in bones, wool, hair, hides, and other animal materials
  • Highly resistant to physical and chemical agents
  • Potential bioterrorism agent because it can be easily grown in large quantities
  • Resistant to destruction and can be formulated into an aerosol for wide dissemination
• Bacillus anthracis


  • Unique capsule comprised of poly-D-glutamic acid and is antiphagocytic
  • 2 plasmid-coded exotoxins: edema toxin and lethal toxin
  • Both are AB type toxins with Activity and Binding domains
  • Binding subunit: protective antigen (protective anthrax vaccines) & mediates cell entry of both toxins
  • Activity subunits: edema and lethal factor
  • Edema factor causes severe edema
  • Lethal factor is responsible for tissue necrosis
  • Lethal factor + protective antigen = lethal toxin
  • Edema factor + protective antigen = edema toxin
• Cutaneous anthrax

  1. Upon introduction of organisms or spores that germinate, a papule develops into a painless, black, severely swollen "malignant pustule," which eventually crusts over

  2. The organisms may invade regional lymph nodes and then the general circulation, leading to fatal septicemia
• Cutaneous anthrax


  95% of human cases
• Pulmonary anthrax (woolsorter's disease)


  1. Caused by inhalation of spores

  2. Progressive hemorrhagic lymphadenitis & hemorrhagic mediastinitis
• Pulmonary anthrax

  Mortality rate of 100% if left untreated
• Vaccine for workers in high-risk occupations
• Post-exposure prophylaxis w/ Ciprofloxacin or Doxycycline
• Bacillus cereus


  Uncommonly, other species of bacillus are implicated in opportunistic lesions, particularly following trauma or the placement of artificial devices and catheters
• Bacillus cereus


  Causes food poisoning by means of enterotoxins with either emetic or diarrheal effects
• Listeria monocytogenes


  The only species of Listeria that infects humans, although the Listeria species are widespread among animals in nature
• Pathogenesis of Listeria monocytogenes

  1. Organism attaches to and enters a variety of mammalian cells, apparently by normal phagocytosis

  2. Once internalized, it escapes from the phagocytic vacuole by elaborating a membrane-damaging toxin called listeriolysin O
• Listeriosis

  Clinical significance of Listeria monocytogenes infections
• Treatments for Listeriosis

  • Ampicillin
  • Trimethoprim/Sulfamethoxazole
• Prevention of Listeriosis through proper food preparation and handling, as well as removal of contaminated products from the food supply